N-pyridyl thiazolesulfenamide vulcanization accelerators



Unite N -PYRIDYL THIIAZOLESULFENAMIDE VULCANIZATION ACCELERATORS Richard Leshin, Akron, Ohio, assignor to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation of Ohio N Drawing. Application August 4, 1955 Serial No. 526,563

13 Claims. (CE. zoo-79.5

grates Patent 0 another object to provide improved compositions for vulcaniz'ing rubber. It is another object to provide vulcanized rubber of improved quality. Other objects will appear hereinafter as the description of the invention proceeds.

According to this invention the acceleration of the vulcanization of rubber with sulfur can be produced by heating rubber and sulfur in the presence of an N-pyridyl thiazolesulfenamide.

The sulfenarnides of this invention are the N-pyridyl thiazolesulfenamides. Various substituted N-pyridyl thiazolesulfenamides are comprehended as part of this invention. Thus included are the benzopyridyl compounds. In addition, the parent compounds can also contain various inert substituents such as alkyl, alkenyl, alkoxy, aryl, aralkyl and aryloxy groups. The 2-pyridyl thiazolesulfenamides and the methyl-Z-pyridyl thiazolesulfenamides constitute the preferred compounds.

The pyridyl thiazolesulfenamides of this invention are readily prepared by reacting a thiazolesulfenamide having an unsubstituted amide (NH group with an amino-pyridine compound as illustrated in Example 1 below.

EXAMPLE 1 Eighteen and five-tenths grams of Z-benzothiazolesulfenarnide and 31 grams of Z-aminopyridine were placed in a 250-milliliter sidearm suction flask, equipped with a thermometer. The thermometer was positioned so that its bulb extended into the mixture of sulfenamide and Z-aminopyridine. The flask was heated by means of a hot water bath and the pressure inside the flask was reduced to about 20 millimeters of mercury pressure by applying a vacuum to the sidearm. As the mixture warmed up it liquefied and foaming started. After the mixture had been heated for about minutes its temperature had risen to 70 to 75 C. and foaming had almost stopped. Heating was stopped. The mixture was allowed to cool to room temperature and the pressure was raised to atmospheric pressure. The mixture was allowed to stand over night at room temperature and wasthen extracted with warm alcohol and filtered. The filtrate was diluted with water and the tan precipitate which formed was filtered, washed with water, and dried. Fifteen grams of product were obtained which, after recrystallization and drying, melted at 134136 C.

The efli'cacy of the compounds of the invention in the vulcanization of rubber is illustrated by the following examples in which representative compounds were used in natural and synthetic rubber as vulcanization accelerators in comparison with N-oxydiethylene-Z-benzothiazolesulfenamide and N-c-yclohexyl-Z-benzothiazolesrilfenamide, both of which are commercial accelerators. in the examples the rubber stocks having the compositions indicated in Examples '2 and '3 were compounded on'a laboratory rubber mill and vulcanized to give the results shown in Tables 1 and 2. The proportions of the ingredients of the rubber compounds are in parts by weight.

EXAMPLE 2 Compound A B C D Smoked Sheets 100. 0 100. 0 100. O 100. 0 HAF Carbon-Black- 50. 0 50.0 50.0 '50. 0 Stearic Acid- 3.0 3. 0 3.0 '3. 0 Zinc Oxide 3.0 3.0 3.0 3.0 5 2. 5 2. 5 2. 5 .0 5. 0 0 5.0 Antioxidant 1. 0 1. 0 0 1. O N oxydiethylene 2 benzothiazo sulfenamide .45 N (2 pyridyl) 2 benz'othiazole- 5 sulfenamide N [2 (3 methylpyridyD] 2 ben zothiazolesulfenamiden 5 N [2 (4 -'methylp'yridyl)] 2 benbenzothiaiz'olesulfenamide 5 Table 1 Ultimate Tensile Strength in Pounds Per Square Inch Modulus at 300% Elongation EXAMPLE 3 Compound E F G GRS 100.0 100. 0 100.0 HAF Carbon Black 50.0 50.0 50. 0 Zinc Oxide 3.0 3.0 3.0 Stearic Acid 3.0 3.0 3.0 Plasticizer" 5. 0 5. 0 5. O Sulfur 1. 1. 75 1. 75 N-cyclohexyl-2benzothiazo ulfenamid 1.0 N (2- yrldyl) -2-benzothiazolenultenamido l. 0 N [2 (4 methylpyridyb] 2 benzothiazolesnlfpnnrnidp 1. 0

3 Table 2 Ultimate Tensile Strength in Pounds Per Square Inch Cure in Minutes at 275 F.

The examples and tables above have illustrated the invention with respect to representative pyridyl-substitutcd thiazolesulfenamides. Other pyridyl-substituted thiazolesulfenamides can also be used, such as the N-(2'pyridyl)- sulfenamides such as N-(2-pyridyl)-2-thiazolesulfenamide; the N-[2-(methylpyridyl)]-sulfenamides such as N [2' (3' methylpyridyl)] 2 thiazolesulfenamide, N [2 methylpyridyl)] 2 benzothiazolesulfenam1de and N- [2-(6-methylpyridyl) l-2-benzothiazolesu1- fenamlde; and the N-benzo[b]pyridyl sulfenamides such as N- 2-benzo [b ]pyridyl) -2-benzothiazolesulfenamide, and b l- (3 -benzo [b] pyridyl -2-benzothiazolesulfenamide.

Various other pyridyl sulfenamides of the invention can be prepared by the method of Example 1 by proper selection of reactants. Representative examples of arnmopyridines that can be used to prepare these materials are Z-aminopyridine, S-aminopyridine, 4-aminopyridine, methyl-substituted isomers of Z-aminopyridine such as 3-methyl-2-aminopyridine, 4methyl-2-aminopyridine, 5:methyl-2-aminopyridine, and 6-methyl-2-aminopyridine; 2-amino-benzo[b]pyridine (i. e. 2-aminoquinol ne), 3-amino-benzo[b]pyridine (i. e. B-aminoquinol ne), 4-amino-benzo[b]pyridine (i. e. 4-aminoquinol ne), l-amino-benzo[c]pyridine (i. e. l-aminoisoquinoline), 3 amino benzo [c] pyridine (i. e. 3 aminoisooumollne), and 4-amino-benzo [c] pyridine (i. e. 4-aminolsoqumoline), and alkyl-substituted derivatives of these amlno-benzopyridines. The 2-aminopyridines constitute a preferred class.

Representative examples of thiazolesulfenamides that can be used are 2-thiazolesulfenamide 4,5-dimethyl-Z-thiazolesulfenamide 4,5-diethyl-2-thiazolesulfenamide 4-methyl-2-thiazolesulfenamide 4-ethyl-2-thiazolesulfenamide 4-butyI-Z-thiazolesulfenamide 4-phenyl-2-thiazolesulfenamide S-ethyl-Z-thiazolesulfenamide 2-benzothiazolesulfenamide 2-naphthothiazolesulfenamide 6-chloro-2-benzothiazolesulfenamide 4-ethoxy-Z-benzothiazolesulfenamide 6-phenyl-2-benzothiazolesulfenamide 6-nitrc-Z-benzothiazolesultenamide 4-methyl-Z-benzothiazolesulfenamide S-ethyl-2-benzothiazolesulfenamide 6-tertiary butyl-Z-benzothiaaolesulfenamide The Z-benzothiazolesulfenamides constitute a preferred class.

The invention has been illustrated in the above examples and tables with respect to natural rubber and GR-S synthetic rubber. Various other rubbers can be used, representative examples being polybutadiene, polyisoprene, the rubbery butadiene-acrylonitrile copolyrners, butadiene-isobutylene copolyrners, butadiene-styrene copolyrners and various other rubbery copolymers of diene hydrocarbons with another monomer copolymerizable therewith.

The amount of accelerator and the curing conditions used in the examples are shown for purposes of illustration. The curing conditions can be varied over the usual range used in the sulfur vulcanization of rubber. The other compounding ingredients also can be varied, and other materials, such as pigments, plasticizers, extenders, oils and waxes, can also be incorporated in the compositions.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. The method of treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolyrners of diene hydrocarbons with another monomer copolymerizable therewith which comprises vulcanizing said rubber with sulfur in the presence of an N-pyridyl-2-thiazolesulfenamide.

2. The method according to claim 1 in which the pyridyl sulfenamide is an N-(Z-pyridyl)-2-thiazolesulfenamide.

3. The method of treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolyrners of diene hydrocarbons with another monomer copolymerizable therewith which comprises vulcanizing said rubber with sulfur in the presence of N-(2'-pyridyl)-2-benzothiazolesulfenamide.

4. The method of treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolyrners of diene hydrocarbons with another monomer copolymerizable therewith which comprises vulcanizing said rubber with sulfur in the presence of N-(3'-benzo[b]pyridyl)-2-benzothiazolesulfenamide.

5. The method of treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolymers of diene hydrocarbons with another monomer copolymerizable therewith which comprises vulcanizing said rubber with sulfur in the presence of N- [2'-(3'-methylpyridyl) ]-2-benzothiazolesulfenamide.

6. The method of treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolymers of diene hydrocarbons with another monomer copolymerizable therewith which comprises vulcanizing said rubber with sulfur in the presence of N-[2(4-methylpyridyl)]-2-benzothiazolesulfenamide.

7. Vulcanized rubber prepared by treating a rubber selected from the group consisting of natural rubber, polybutadiene, polyisoprene and rubbery copolymers of diene hydrocarbons with another monomer copolmerizable therewith with sulfur in the presence of an N-pyridyl- 2-thiazolesulfenamide.

8. As a new compound an N-pyridyl-2-thiazolesulfenamide.

9. As a new compound an N2'-pyridyl-2-thiazolesu1- fenamide.

10. As a new compound N-(2-pyridyl)-2-benzothi- .awlesulfenamide.

11. As a new compound N-[2'-(3-methylpyridyl)]-2- References Cited in the file of this patent benzothiazolesulfenamide.

12. As a new compound N-[2-(4'-methylpyridy1)]-2- UNITED STATES PATENTS benzothiazolesulfenamide, 2,417,989 Moore 1947 13. A vulcanizable composition comprising a rubber 5 2,419,283 Paul 1947 selected from the group consisting of natural rubber, 2,419,294 Skaptason p 22,1947 polybutadiene, polyisoprene and rubbery copolymers of 2,461,953 Bargmeyer 15, 1949 diene hydrocarbons with another monomer copolmeriz- 2,476,818 Carr y 1949 able therewith, sulfur and an N-pyridyl-2-thiazolesu1fen- 2,666,043 Carr 1954 amide 10 2, 1, 1 Gregory Oct. 5, 1954 OTHER REFERENCES Carr: Journal of Organic Chemistry, vol. 14, pages 921-934 (only page 927 relied upon) (1949). 

1. THE METHOD OF TREATING A RUBBER SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, POLYBUTADIENE, POLYISOPRENE AND RUBBERY COPOLYMERS OF DIENE HYDROCARBONS WITH ANOTHER MONOMER COPOLYMERIZABLE THEREWITH WHICH COMPRISES VULCANIZING SAID RUBBER WITH SULFUR IN THE PRESENCE OF AN N-PYRIDYL-2-THIAZOLESULFENAMIDE.
 8. AS A NEW COMPOUND AN N-PYRIDYL-2-THIAZOLESULFENAMIDE. 